This invention relates generally to couplings for shafts that provide isolation of noise, vibration and harshness, and, more particularly, to such couplings that are suitable for motor vehicle steering columns.
Typically, motor vehicle steering columns include a disk type isolator that comprises a rubber disk that is mounted between two shafts. The shafts have radially extending arms that are fixed to the disk, the radially extending arms of the two shafts being displaced 90 degrees from each other. Such isolators are effective in providing acceptable levels of radial, axial and torsional compliance. However, the high complexity and large size of such devices makes them expensive to produce and too bulky to fit within modern compact steering column assemblies.
Alternatively, motor vehicle steering columns have used a tubular bushing type isolator. Typically, one shaft is pinned within a sleeve or tubular yoke that is fixed to a second shaft, and a rubber or elastomer bushing is positioned therebetween. Such isolators provide a desired compact size and reduced cost compared to disk type isolators. However, the tubular bushing type isolators do not provide sufficient torsional stiffness. More specifically, when the bushing provides sufficient compliance in the radial and axial directions, the torsional compliance is unacceptable.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.